USBNET: A story of networking and threads that won't stop pulling


August 13, 2019 posted by matthew green

Once upon a time a developer wrote a temperature sensor driver for one system and decided to port it to another, similar, system. For days and then weeks, the developer waited and waited for the other, similar, system to arrive.

One day, joy of joys, the other, similar, system arrived. A National Day of Celebration commenced, and the porting effort began. Over hours, perhaps even as many as five hours of time, the sensors were finally able to tell you whether they were hot or not.

This other, similar, system suddenly was purposeless and was pondering what else life could provide when the Remote Server task popped up and said "Hey, first media file is free", and sadly, this other, similar, system tried its first media file, and then purchased many, many more media files, and suddenly this other, similar, system was suddenly hooked.

Unfortunately, this other, similar, system had a problem talking on the network without falling asleep on the job, so the developer says "let's try a USB network instead!", and initially this seemed like a good idea. Many bits were transferred over USB, but soon whispers of a lurking monster, known to developers, experience or otherwise, as KASSERT, were heard and soon found common.

The developer attempted other USB network as the other, similar, system was destined to be flown many thousands of miles away soon, but the only other option was similarly plagued by the KASSERT monster. The developer reached into his Bag Of Holding and pulled out a magical weapon known capable of slaying the KASSERT monster. The mighty blade of MPSAFE was free again!

After much planning and many failed attacks, the developer was able to slay the KASSERT monster and all the bits wanting to be transferred were able to be.

For a day and for a night there were celebrations. Much food and ale was consumed until finally everyone was asleep, and the music and lights were finally turned off. In the morning a great clean up was needed and while the developer was cleaning off the shiny, happy and working USB network the original USB network was accidentally reconnected. Oh no, the KASSERT monster has returned! Lock your doors and hide your children.

The developer quickly pulled out MPSAFE again, and once again the KASSERT monster was slain, though the face of this monster was different to the previous monster. The developer then searched and searched for surely they were more KASSERT monsters to be found. Indeed, many many others were found, though they retreated to safety after two more of their number were slain by the mighty MPSAFE.

The developer called upon his friends Shared and Code and with them forged a new weapon against the KASSERT monster, using the mighty MPSAFE in ways unheard of before. After much research and planning, and with the help of some friends, the USBNET was born. All the angels and all the birds of the world were said to sing all at once at this moment, for the USBNET would bring happiness to both the Code Deletionist and the Code Sharers, bound to war against each other from time immemorial.

With this new USBNET the developer was able to blaze a trail across the landscape, searching out each KASSERT monster lurking in every USB network corner. All told, fourteen faces of KASSERT monster were found and the developer and his friends have slain seven of these faces, with the remaining seven under attack, life looks grim for them.

The other, similar, system is safe now. Turns out that MPSAFE also has cleared up the sleeping problem using the cousins, NET and FDT in a tight, dual-blade combination.

Let the world rejoice, for soon the KASSERT monster will be no more!

--mrg @ 2019-08-11

tl;dr:

i fixed many bugs across several USB ethernet adapters and got sick of fixing the same bug across multiple drivers so made common code for them to use instead. the original 4 drivers fixed were axen(4), axe(4), cdce(4), and ure(4). the current list of fixed drivers, at time of writing, includes smsc(4), udav(4) and urndis(4). all drivers except umb(4) are ported but either not tested or not yet working with the usbnet(9) framework.

update 2019-09-02:

all 13 known working drivers converted and will be present in netbsd 9.

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